In a hydraulic machine with a toothed set comprising a toothed ring with an inner toothing, whose circumferential surface extends in parallel with its axis, and a gear wheel with an outer toothing, whose circumferential surface extends in parallel with its axis, at least one tooth flank having an edge as an axial end of a section, which is located between the circumferential surface and a surface directed radially inwards. Such a machine is, for example, known from EP 0 959 248 A2. This machine has clearances or recesses, which can, for example, be made by milling. They are located on both tooth flanks of each tooth of the outer toothing of the gear wheel and are used for a so-called secondary commutation, during which a brief connection to one of the neighbouring pressure chambers is ensured shortly before any pressure chamber reaches a minimum or a maximum volume. At the time of the commutation it is ensured that no connection exists between the pressure chamber in question with maximum or minimum volume, respectively, and the corresponding neighbouring pressure chambers. Thus, a stable operation with low speeds and high pressures should be achieved. At the axial ends of the clearances and at the front edges, the circumferential surfaces extend over edges into end faces of the clearances or the front side of the gear wheel, respectively.
Such machines now turn out to have problems with wear in some areas of the toothed set.